Added System.Memory.dll

So we can use Span and Memory from System

Author: 89netraM

wasm/LinkerConfig.xml

@@ -6,4 +6,5 @@
 	<assembly fullname="System.Core" />
 	<assembly fullname="System.Collections" />
 	<assembly fullname="System.Net.Http" />
+	<assembly fullname="System.Memory" />
 </linker>

wasm/Program.cs

@@ -24,7 +24,8 @@ public static class Program
 			"System",
 			"System.Core",
 			"System.Collections",
-			"System.Net.Http"
+			"System.Net.Http",
+			"System.Memory"
 		);
 		private static readonly IEnumerable<string> defaultUsings = new[]
 		{